diff --git a/sandbox/grist/column.py b/sandbox/grist/column.py
index e3d51951..d9625dff 100644
--- a/sandbox/grist/column.py
+++ b/sandbox/grist/column.py
@@ -358,6 +358,10 @@ class PositionColumn(NumericColumn):
     # This is a list of row_ids, ordered by the position.
     self._sorted_rows = SortedListWithKey(key=lambda x: SafeSortKey(self.raw_get(x)))
 
+  def clear(self):
+    super(PositionColumn, self).clear()
+    self._sorted_rows.clear()
+
   def set(self, row_id, value):
     self._sorted_rows.discard(row_id)
     super(PositionColumn, self).set(row_id, value)
diff --git a/sandbox/grist/test_replace_table_data.py b/sandbox/grist/test_replace_table_data.py
new file mode 100644
index 00000000..357b0407
--- /dev/null
+++ b/sandbox/grist/test_replace_table_data.py
@@ -0,0 +1,47 @@
+import logging
+
+import test_engine
+from test_engine import Table, Column
+
+log = logging.getLogger(__name__)
+
+class TestReplaceTableData(test_engine.EngineTestCase):
+
+  @test_engine.test_undo
+  def test_replace_and_add(self):
+    # This tests a fix for a bug where after ReplaceTableData, subsequent adds were causing an
+    # error with "relabeling" (updating manualSort column).
+
+    # Add a table with a couple of columns and records.
+    self.apply_user_action(["AddTable", "Vessels", []])
+    self.apply_user_action(["AddColumn", "Vessels", "Type", {}])
+    self.apply_user_action(["AddColumn", "Vessels", "Size", {}])
+    self.apply_user_action(["BulkAddRecord", "Vessels", [None, None],
+      {"Type": ["cup", "pot"], "Size": [8, 64]}])
+
+    # Check that we guessed correct column types, and the values are there.
+    self.assertTables([
+      Table(1, "Vessels", primaryViewId=1, summarySourceTable=0, columns=[
+        Column(1, "manualSort", "ManualSortPos",  False, "", 0),
+        Column(2, "Type",       "Text",           False, "", 0),
+        Column(3, "Size",       "Numeric",        False, "", 0),
+      ])
+    ])
+    self.assertTableData("Vessels", cols="subset", rows="all", data=[
+      [ "id", "Type", "Size"  ],
+      [ 1,    "cup",     8    ],
+      [ 2,    "pot",    64    ],
+    ])
+
+    # Now do ReplaceTableData, and add more rows.
+    self.apply_user_action(["ReplaceTableData", "Vessels", [], {}])
+
+    # The bug used to happen here, manifesting as error
+    # "docactions.[Bulk]UpdateRecord for non-existent # record #1"
+    self.apply_user_action(["BulkAddRecord", "Vessels", [None, None],
+      {"Type": ["shot", "bucket"], "Size": [1.5, 640.0]}])
+    self.assertTableData("Vessels", cols="subset", rows="all", data=[
+      [ "id", "Type",   "Size"  ],
+      [ 1,    "shot",     1.5   ],
+      [ 2,    "bucket",   640   ],
+    ])
diff --git a/test/nbrowser/gristUtils.ts b/test/nbrowser/gristUtils.ts
index 8a6dade6..695afc92 100644
--- a/test/nbrowser/gristUtils.ts
+++ b/test/nbrowser/gristUtils.ts
@@ -2824,9 +2824,12 @@ export async function onNewTab(action: () => Promise<void>) {
   await driver.executeScript("window.open('about:blank', '_blank')");
   const tabs = await driver.getAllWindowHandles();
   await driver.switchTo().window(tabs[tabs.length - 1]);
-  await action();
-  await driver.close();
-  await driver.switchTo().window(tabs[tabs.length - 2]);
+  try {
+    await action();
+  } finally {
+    await driver.close();
+    await driver.switchTo().window(tabs[tabs.length - 2]);
+  }
 }
 
 /**